Method of preparing (perfluoroalkyl) ethyl acrylic esters and methods of preparing copolymers using said esters

ABSTRACT

A polyfluoroalkyl iodide is reacted with a (meth)acrylic acid metal salt to form a corresponding polyfluoroalkyl (meth)acrylate ester. The polyfluoroalkyl (meth)acrylate ester is separated from the reaction product through the evaporation, so that the ester is recovered. According to the present method, the polyfluoroalkyl iodide is reacted with the (meth)acrylic acid metal salt without introducing water, thus making it possible to prepare a polyfluoroalkyl (meth)acrylate ester. The resulting ester can also be used to copolymerize an ethylenically unsaturated compound capable of copolymerizing with the ester.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP00/04201 which has an Internationalfiling date of Jun. 27, 2000, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a first method of preparing apolyfluoroalkyl (meth)acrylate ester, and a second method of preparing afluorine-containing acrylic copolymer using the ester obtained by thefirst method.

RELATED ART

A (meth)acrylate ester having a perfluoroalkyl group and afluorine-containing acrylic copolymer obtained through copolymerizationof the (meth)acrylate ester and a monomer, which is capable ofcopolymerizing with the ester, have been used to impart water- andoil-repellency to textile products.

A polyfluoroalkyl (meth)acrylate ester to be used as a raw material inan industrial method of preparing such a fluorine-containing acryliccopolymer has conventionally been prepared by an operation as follows:

A polyfluoroalkyl iodide having a perfluoroalkyl group corresponding tothe above ester is reacted with a (meth)acrylic acid metal salt (forexample, potassium salt) in a proper solvent (for example, tert-butanol)(for example, in an ester-forming reaction apparatus 60 in FIG. 2) toobtain, as a reaction product, a suspension containing thepolyfluoroalkyl (meth)acrylate ester and the metal iodide (for example,potassium iodide) precipitate derived from the (meth)acrylic acid metalsalt. Then, the suspension is subjected to a filtration to separate themetal iodide (potassium iodide) as a solid material from a filtrate. Thefiltrate is thereafter subjected to a distillation to obtain thepolyfluoroalkyl (meth)acrylate ester by separating the solvent(tert-butanol), which solvent may be then recycled.

According to the method described above, as shown in FIG. 2, in the stepof filtering the metal iodide in a filtering apparatus 70, aproduct-based suspension is filtered and co-washed with a solvent, andthereby the polyfluoroalkyl (meth)acrylate ester in a filter cake isdissolved and recovered. Then, water is added to the filter cake and themetal iodide is discharged from the filtering apparatus in the form ofan aqueous solution, while the filtering apparatus 70 is dried byheating for the following filtering step. The product-based filtrateseparated previously is mixed with the solvent used for co-washing andthe mixture is transferred to an evaporator 80, where the solvent andthe polyfluoroalkyl (meth)acrylate ester are distilled off in order by adistillation operation, thereby to obtain a polyfluoroalkyl(meth)acrylate ester as a desired product, in an ester receiver 90 andto recover the solvent in a solvent tank 100.

DISCLOSURE OF INVENTION

According to the method including such a filtering step, since the metaliodide is discharged from the filtering apparatus 70 in a form ofaqueous solution thereof by addition of water to the filter cake of themetal iodide, a small amount of water is introduced into the solvent inthe following filtering step of the product-based suspension, resultingin incorporation of water along with the solvent into the reactionproduct. This water is easily miscible with the solvent such astert-butanol and then accumulated in the solvent after being introducedinto the solvent. In the case where a dehydration operation of thesolvent is not carried out, water is circulated along with the solventto the ester-forming reaction step.

However, since water inhibits the reaction of forming thepolyfluoroalkyl (meth)acrylate ester from the polyfluoroalkyl iodide andthe (meth)acrylic acid metal salt, the existence of water in the solventis not preferable. Therefore, it was required to carry out a dehydrationtreatment if the water content in the solvent was increased beforeintroducing the solvent into the ester-forming reaction step.

Accordingly, if the polyfluoroalkyl (meth)acrylate ester can be preparedwithout introducing water into the reaction system, the yield of theester-forming reaction can be improved, and furthermore, the operationof dehydrating the solvent can be omitted, thus turning to its advantagein view of equipment cost.

An object of the present invention is to solve the problems describedabove and to provide a method of preparing a polyfluoroalkyl(meth)acrylate ester, which is to be used as a raw material of afluorine-containing acrylic copolymer, without introducing water intothe reaction system.

The present invention provides, in one aspect, a method of preparing apolyfluoroalkyl (meth)acrylate ester, which comprises the steps of:

(I) reacting a polyfluoroalkyl iodide with a (meth)acrylic acid metalsalt to obtain a reaction mixture containing a polyfluoroalkyl(meth)acrylate ester and a metal iodide, as shown by the reaction scheme(Formula 1):

C_(n)F_(2n+)CH₂CH₂I+CH₂═CXCOOM→

C_(n)F_(2n+)CH₂CH₂OCOCX═CH₂+MI  (Formula 1)

[wherein X represents H or CH₃, n represents an integer within a rangefrom 2 to 26, preferably from 8 to 20, and most preferably from 8 to 14,and M represents an alkali metal element]; and

(II) heating the obtained reaction mixture to evaporate thepolyfluoroalkyl (meth)acrylate ester, thereby to separate and recoverthe polyfluoroalkyl (meth)acrylate ester.

The present invention provides, in another aspect, a method of preparinga fluorine-containing acrylic copolymer, which comprises the step (step(III)) of copolymerizing the polyfluoroalkyl (meth)acrylate esterprepared by the method described above with an ethylenically unsaturatedcompound capable of copolymerizing with the above ester.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration showing an embodiment of an apparatuswhich can be used to effect the method of preparing a polyfluoroalkyl(meth)acrylate ester of the present invention.

FIG. 2 is a schematic illustration showing an embodiment of an apparatuswhich can be used to effect the method of preparing a polyfluoroalkyl(meth)acrylate ester of the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Describing with reference to the accompanying drawings, the step (I) ofthe method of preparing a fluorine-containing acrylic copolymeraccording to the present invention is carried out in an ester-formingreaction apparatus 10 shown in FIG. 1. In the ester-forming reactionapparatus 10, a polyfluoroalkyl iodide represented by the formula 2:

C_(n)F_(2n+1)CH₂CH₂I  (Formula 2)

[wherein n represents an integer within a range from 2 to 26, andpreferably from 8 to 20]

and a (meth)acrylic acid metal salt, as raw materials, are charged andthen the ester-forming reaction is carried out to obtain apolyfluoroalkyl (meth)acrylate ester represented by the formula 3:

C_(n)F_(2n+1)CH₂CH₂OCOCX═CH₂  (Formula 3)

[wherein X represents H or CH₃].

A polyfluoroalkyl group in the polyfluoroalkyl iodide used herein has astructure that an ethylene group (CH₂CH₂) is added to a polyfluoroalkylgroup (C_(n)F_(2n+1)). Most preferably, n is an integer within a rangefrom 8 to 14.

The (meth)acrylic acid metal salt may be a metal salt such as sodium,potassium or lithium salt, and preferably a potassium salt.

Examples of the solvent, which can be used in this reaction step includen-butanol, sec-butanol, tert-butanol, amyl alcohol, tert-amyl alcohol,methyl isobutyl ketone, isopropyl alcohol, methyl ethyl ketone, amylacetate, and acetonitrile. Among these solvents, tert-butanol isparticularly preferable.

This reaction step can be carried out at a temperature within a rangefrom 150 to 220° C. for 60 to 300 minutes by controlling a molar ratioof raw materials [molar ratio of the (meth)acrylic acid metal salt tothe polyfluoroalkyl iodide] within a range from 1.0 to 1.25, preferablyfrom 1.0 to 1.05, and controlling the water content in the reactionsystem within a range from 0.01 to 1.0% by weight, preferably 0.1% byweight or less.

In the step (II) of the method according to the present invention, thereaction product system from the step (I) containing the solvent, themetal iodide (MI) and the polyfluoroalkyl (meth)acrylate ester as thedesired product is transferred to an evaporator 20 as shown in FIG. 1,where the solvent and the polyfluoroalkyl (meth)acrylate ester areseparated from the metal iodide (MI) by evaporating them, and then MIand a material having a boiling point higher than that of the desiredproduct, which may exist in certain cases, are substantially recoveredin a MI receiver 30 as a residue.

Since the reaction product system, which is subjected to thisevaporation operation, contains the solvent at an earlier stage of theoperation and is in a heated state, the (meth)acrylic polyfluoroalkylester is in a molten state or a solution state of being partiallydissolved in the solvent and the metal iodide is in a state of beingsuspended in the solution. Therefore, the viscosity of the system islow.

However, as evaporation operation of the solvent and the (meth)acrylicpolyfluoroalkyl ester proceeds, the solvent disappears from the productsystem earlier than the (meth)acrylic polyfluoroalkyl ester because thesolvent generally has a boiling point lower than that of the(meth)acrylic polyfluoroalkyl ester. The(meth)acrylic polyfluoroalkylester having a small numerical value of n (Formula 3), namely, thosehaving a lower boiling point are evaporated and the content of thoseesters in the product system is gradually reduced. Then, since it turnsinto a condition where the metal iodide is suspended in the(meth)acrylic polyfluoroalkyl ester having a large numerical value of n,namely, the (meth)acrylic polyfluoroalkyl ester having a higher boilingpoint and higher melting point, the viscosity of the system is graduallyincreased.

Since the solvent is evaporated earlier than the (meth)acrylicpolyfluoroalkyl ester in the operation of recovering the solvent and the(meth)acrylic polyfluoroalkyl ester, the solvent is taken out first andthen recovered in a solvent tank 50 after necessary cooling orcondensing. The (meth)acrylic polyfluoroalkyl ester component, which isevaporated thereafter, is recovered in an ester receiver 40 afternecessary cooling or condensing. Usually, the boiling point of thesolvent is about 80° C. and that of the (meth)acrylic polyfluoroalkylester is about 190° C. so that the difference in boiling point betweenthe solvent and the ester is large. Therefore, the solvent and the(meth)acrylic polyfluoroalkyl ester are recovered in order by so-calledsimple distillation to obtain MI as a bottom, thus making it possible tocarry out the recovering operation. Alternatively, the operation ofevaporating the solvent and the (meth)acrylic polyfluoroalkyl ester andrecovering them may be carried out by recovering both the solvent andthe (meth)acrylic polyfluoroalkyl ester together by evaporation,followed by separating and recovering the (meth)acrylic polyfluoroalkylester from the solvent by distillation.

In the method of the present invention, only the polyfluoroalkyl(meth)acrylate ester is evaporated from a mixture of the polyfluoroalkyl(meth)acrylate ester and the metal iodide as the solid component afterthe solvent was completely evaporated (or distilled off), so that theliquid component is separated from the solid component by evaporatingthe liquid component. Therefore, the expression “the polyfluoroalkyl(meth)acrylate ester is evaporated” is used in the present descriptionand claims.

In the case when the polyfluoroalkyl group isC_(n)F_(2n+1)CH₂CH₂OCOCH═CH₂ (n=8 to 20) in the system in whichtert-butanol as the solvent, the polyfluoroalkyl (meth)acrylate esterand potassium iodide as the metal iodide exist in a ratio (on a weightbasis) of 30:55:15, the viscosity of the system is within a range from0.5 to 20 cP (centipoise) at the temperature of 100° C. Then, in thesystem in which the polyfluoroalkyl (meth)acrylate ester and the metaliodide exist in a ratio (on a weight basis) of 5:95 after all of thesolvent and almost all of the polyfluoroalkyl (meth)acrylate ester areevaporated from this system, the viscosity of the system becomes 500 cPor more at the temperature of 100° C.

Accordingly, the evaporating operation of the present invention requiresto use an evaporator which has a outstanding stirring efficiency and aheat-transfer efficiency to an object to be evaporated. Althoughevaporation can be carried out under a normal atmospheric pressure, itis preferable to lower the evaporation temperature by evaporating undera reduced pressure in order to have a material having a higher boilingpoint be evaporated.

In the case where the polyfluoroalkyl group is C₁₂F₂₅CH₂CH₂OCOCH═CH₂,the boiling point of the polyfluoroalkyl (meth)acrylate ester is about170° C. at about 25 mmHg, and therefore, an evaporator capable ofreducing the pressure to 1 to 25 mmHg is preferably used in theevaporating operation of the present invention. To carry out theevaporating operation at further lower temperature, it is preferred touse an evaporator capable of reducing the pressure to 1 to 15 mmHg, andmore preferably 1 to 10 mmHg.

Accordingly, it is important to use an apparatus having an excellentheat transfer efficiency and a stirring efficiency as the evaporator inthe step (II) of the present invention. It is preferred to use anevaporator having a jacketed heating means, having a helical blade asthe stirring blade and also having a reverse conical shape at the lowerportion of the evaporator.

Examples of such an evaporator include Vertical Cone Reactor(manufactured by Mitsubishi Heavy Industries., Ltd), Advanced RibbonReactor (manufactured by Mitsubishi Heavy Industries., Ltd), and SuperBlend (manufactured by Sumitomo Heavy Industries, Ltd.). Vertical ConeReactor is equipped with a corn-shaped tank and a helical blade having aspirally-wound ribbon-shaped stirring blade.

In the case where the step (II) is carried out using Vertical ConeReactor, the solvent is evaporated by heating to about 120 to 145° C.under a pressure such as about normal atmospheric pressure and RfCH=CH₂is evaporated by reducing the pressure to about 300 to 500 mmHg whilemaintaining the temperature, and then the pressure is reduced to about 5to 10 mmHg and the temperature is increased to about 170 to 200° C.,thereby to evaporate the (meth)acrylic polyfluoroalkyl ester, thusmaking it possible to separate MI. For example, in case ofC₈F₁₇CH₂CH₂OCOCH═CH₂, the temperature is increased to 135° C. under apressure of 0.01 MPa (gauge pressure) to obtain a solvent, followed byrecovering RfCH═CH₂ as a by-product at −400 mmHg (gauge pressure). Andthen, the pressure is reduced to about −755 mmHg and the temperature isincreased to 190° C. to obtain an polyfluoroalkyl acrylate ester. Then,the contents of the evaporator are cooled to 50° C. or lower to recoverMI.

The (meth)acrylic polyfluoroalkyl ester can be prepared in the mannerdescribed above. The recovered solvent can be recycled to theester-forming reaction step without further treatment because itcontains substantially no water.

In the step of the method of preparing a polymer according to thepresent invention, a fluorine-containing acrylic copolymer is preparedby copolymerizing the polyfluoroalkyl (meth)acrylate ester, which wasobtained through the first method of preparing the polyfluoroalkyl(meth)acrylate ester, with an ethylenically unsaturated compound capableof copolymerizing with the above polyfluoroalkyl (meth)acrylate ester.

In the copolymerization reaction, a polyfluoroalkyl (meth)acrylate esterrepresented by the formula 3, n being within a range from 6 to 22 may beused.

Specific examples of the ethylenically unsaturated compound (monomer),which is copolymerized with the polyfluoroalkyl (meth)acrylate ester inthe second a method of preparing the fluorine-containing acryliccopolymer, are compounds included in the following groups (a), (b) and(c). However, the ethylenically unsaturated compound is not limited tothese examples, and may be basically an ethylenically unsaturatedcompound capable of copolymerizing with a (meth)acrylic acid.

Examples of the group (a) include ethylene, vinyl acetate, vinylchloride, vinylidene halide, (meth)acrylic acid, (meth)acrylonitrile,styrene, α-methylstyrene, p-methylstyrene, (meth)acrylamide, N-methylol(meth)acrylamide, hydroxymethyl (meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl(meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol(meth)acrylate, methoxypolyethylene glycol (meth)acrylate,methoxypolypropylene glycol (meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, glycidyl(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl(meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentenyl(meth)acrylate, hydroxypropyltrimethylammonium chloride methacrylate,ethyltrimethylammonium chloride methacrylate, vinyl alkyl ether, alkylvinyl ether halide, butadiene, isoprene, chloroprene, and maleicanhydride.

Examples of the group (b) include acrylates represented by the generalformula (Formula 4):

CH₂═CA¹COOA²  (Formula 4)

[wherein A¹ represents a hydrogen atom or a methyl group, and A²represents an alkyl group represented by C_(m)H_(2m+1) (m represents aninteger of 1 to 30)].

Examples of the group (c) include compound represented by the formula 5:

manufactured by KYOEISHA CHEMICAL Co., LTD. under the trade name ofLIGHT-ESTER G), compound represented by the formula 6:

(manufactured by KYOEISHA CHEMICAL Co., LTD. under the trade name ofLIGHT-ESTER CL), compound represented by the formula 7:

(manufactured by DOW CORNING TORAY SILICONE CO., LTD. under the tradename of SZ6030), compound represented by the formula 8:

compound represented by the formula 9:

and compound (sulfonic acid-containing monomer) represented by theformula 10:

(n=1 to 20).

In the copolymerization according to the method of preparing thefluorine-containing acrylic copolymer, one or two or more kinds of thepolyfluoroalkyl (meth)acrylate esters may be copolymerized with one ortwo or more kinds of the ethylenically unsaturated compounds.

The reaction or operation of the copolymerization to be carried outaccording to the method of preparing the fluorine-containing acryliccopolymer is basically a known reaction and is disclosed, for example,in Japanese Patent Kokai Publication No. 10-212325.

In the copolymerization reaction carried out according to the presentmethod of preparing the fluorine-containing acrylic copolymer, bulkpolymerization, solution polymerization, suspension polymerization andemulsion polymerization methods can be used. Among these methods, anemulsion polymerization method is particularly preferred becauseproducts are often used in the presence of a water medium.

The resulting copolymer may be used in water and oil repellents as wellas textile processing agents because the copolymer has improvedproperties in various characteristics such as stain proof propertiessuch as decontaminability, water and oil repellency, and dyeingresistance, antistatic property, antifungal property, abrasionresistance, cleaning resistance, feeling, and dispersion stability tomedium such as water. Therefore, the kind and proportion of each of thepolyfluoroalkyl (meth)acrylate ester and the ethylenically unsaturatedcompound to be used in the copolymerization can be selected according tothe purposes.

The emulsion polymerization is carried out in an aqueous medium andwater as the medium is used in the amount within a range from about 1 to3 parts by weight, and preferably from about 1.5 to 2.5 parts by weight,based on 1 part by weight of the sum total of the monomer componentsused in the polymerization.

As an emulsifier used in emulsification, various known emulsifiersselected from anionic, cationic, nonionic and amphoteric emulsifiers canbe used. The emulsifier is used in the amount within a range from about0.02 to 0.15 parts by weight, and preferably from about 0.07 to 0.10parts by weight, based on 1 part by weight of the sum total of themonomer components used in the polymerization.

As a polymerization initiator, there can be used those which aregenerally used. For example, various polymerization initiators such asazo-type or peroxide-type polymerization initiators can be used. Thepolymerization initiator is used in an amount within a range from about0.001 to 0.05 parts by weight, and preferably from about 0.008 to 0.012parts by weight, based on 1 part by weight of the sum total of themonomer components used in the polymerization.

The emulsifying operation before the copolymerization, which is carriedout according to the method of preparing the fluorine-containing acryliccopolymer, is generally carried out at the temperature within a rangefrom 40 to 80° C., and preferably from 50 to 60° C., in view of physicalproperties, especially melting point, of the polyfluoroalkyl acrylateester and ethylenically unsaturated compound as raw materials of thecopolymer. The solid content in the system to be emulsified ispreferably within a range from 5 to 65%, and preferably from 20 to 40%(based on the total weight).

In the method of preparing the fluorine-containing acrylic copolymer, anemulsifying treatment of a solution to be treated, comprising a mixtureof the polyfluoroalkyl (meth)acrylate ester and the ethylenicallyunsaturated compound, which are to be copolymerized, is carried out byusing a high-pressure emulsifying apparatus to form emulsion particleshaving a particle size within a range from 0.001 to 1 μm, preferablyfrom 0.01 to 0.5 μm, and most preferably from 0.01 to 0.2 μm. The reasonwhy the particle size of the emulsion particles is controlled to about 1μm or less before the copolymerization is as follows. That is, whenemulsion particles having a particle size more than 1 μm exist in thesystem to be polymerized in the polymerization operation, coagulates areliable to be formed. By setting the maximum particle size of theemulsion particles to 1 μm or less, formation of coagulates may beprevented, thereby making it possible to carry out stable emulsionpolymerization and to distribute the desired copolymer product withinthe particles of the emulsion polymer product almost uniformly.

To achieve such emulsification, a high-pressure emulsifying apparatussuch as Gaulin Homogenizer (Manton Gaulin Laboratory Homogenizer 15M-6TAmanufactured by Gaulin Inc.) or ultra-fine particles dispersionemulsifying apparatus) (Microfluidizer MIIO-E/H manufactured byMicrofluidics Corp. or Mizuho-Kogyo, Co. Ltd.) can be used incombination with a conventional emulsifying apparatus, which employs ashear action, such as homomixer (T.K. Homomixer Mark II manufactured byTokusyu Kika Kogyo Co., Ltd.) or ultramixer (vacuum stirring apparatusmanufactured by Mizuho-Kogyo Co., Ltd.).

When using GAULIN HOMOGENIZER in the emulsification of the step (III) ofthe present invention, emulsification can be carried out by colliding amixture to be emulsified against a metal plate at a pressure within arange from 150 to 700 kg/m², and generally 400 kg/m² on average. Whenusing Microfluidizer, emulsification can be carried out at the pressurewithin a range from 200 to 2000 kg/m², and generally from 1500 to 2000kg/m².

Microfluidizer generally used is that of a liquid-liquid collision type(Y type chamber) in comparison with GAULIN HOMOGENIZER, and the emulsioncan be controlled by using in combination with a Z type one for backpressure. This apparatus is a high-pressure emulsifying apparatus havingsuch advantages that the mechanical noise thereof is small and aconstant pressure is available since it employs a hydraulic pressure tosecure a high pressure.

When a common solution is applied to the emulsification using aconventional dispersion mixer such as homomixer or ultramixer and ahigh-pressure emulsifying machine, respectively, emulsion particleshaving an particle size within a range from about 0.7 μm to 1.0 mm areobtained and it is scarcely expected that the upper limit value of theemulsion particles is controlled to 1 μm in the former case. On theother hand, in the latter case using the high-pressure emulsifyingmachine, emulsion particles having an particle size within a range fromabout 0.01 to 0.5 μm are obtained, thus making it possible to controlthe upper limit value of the emulsion particles to 1 μm.

Therefore, the high-pressure emulsifying machine is preferably used inthe emulsifying treatment which is carried out in the method ofpreparing the fluorine-containing acrylic copolymer of the presentinvention. In the case where the solution to be treated, which is to beemulsified, exists in a large amount, even if the solution to be treatedin a condition of forming a mixture to be emulsified is directlyintroduced into the high-pressure emulsifying machine, it takes a longtime to obtain emulsion particles having a desired uniform particlesize, for example, a particle size within a range from about 0.01 to 0.5μm, resulting in poor efficiency. Therefore, a conventional dispersionmixer (homomixer or ultramixer) can be used in combination with thehigh-pressure emulsifying apparatus. In such a case, a conventionalemulsifying apparatus can also be used in pre-treatment of high-pressureemulsification. Alternatively, a conventional emulsifying apparatus canbe connected in series or in parallel with the high-pressure emulsifyingapparatus through arranging conduits.

INDUSTRIAL APPLICABILITY

According to the method of preparing a polyfluoroalkyl (meth)acrylateester of the present invention, the yield of the ester-forming reactionwas enhanced from 80% to 88% by preventing water from introducing intothe reaction system. The recovered solvent (tert-butanol) could berecycled to the ester-forming reaction step without further treatmentbecause it was free from water.

Accordingly, it has been found that the constitution of the method ofpreparing a polyfluoroalkyl (meth)acrylate ester of the presentinvention can be made simple as compared with a conventional preparationmethod, and furthermore, the polyfluoroalkyl (meth)acrylate ester can beprepared advantageously as compared with the prior art, with respect tothe yield and equipment cost.

As described above, the quality of the copolymer obtained by the methodof preparing a fluorine-containing acrylic copolymer of the presentinvention is improved by employing high-pressure emulsification.

EXAMPLES Example 1

Step (I):

Using, as a reaction apparatus, a pressure-resistant (proof pressure: 30kg/cm²) SUS autoclave (volume: 1 liter) equipped with a high-efficiencystirring blade “FULLZONE” (manufactured by Shinko Pantec Company Ltd.),C₈F₁₇CH₂CH₂I (500 g), potassium acrylate (93 g) and tert-butanol (350 g)were charged in this reaction apparatus and the ester-forming reactionwas carried out.

In the ester-forming reaction step, the ester-forming reaction wascarried under the conditions of a temperature of 175 to 185° C. for 3.0to 4.0 hours. The analysis results of the product in the ester-formingreaction are as follows. An analysis by means of gas chromatography (GC)using a column SE-30 (3 m) revealed that (1) a conversion ratio ofC₈F₁₇CH₂CH₂I is 99.8%; and (2) a yield of C₈F₁₇CH₂CH₂OCOCH═CH₂ is 88%, ayield of C₈F₁₇CH═CH₂ is 10%, and a yield of C₈F₁₇CH₂CH₂OH is 1% or less.As a result of the measurement by means of gas chromatography, the yieldof a polyfluoroalkyl acrylate ester was 88%.

Step (II):

The reaction product (943 g) from the above step (I) was transferred toVertical Cone Reactor having a volume of 1 liter and heated to 135° C.under normal pressure, thereby to recover 340 g of tert-butanol. Then,the pressure was reduced to 360 mmHg (gauge pressure: −400 mmHg) whilemaintaining the temperature to recover RfCH═CH₂ as by-products. Then,after reducing the pressure to about 5 mmHg, stirring was carried outwhile raising the temperature to about 190° C. by jacket heating,thereby to evaporate the liquid component.

The gas component discharge portion of Vertical Cone Reactor may beprovided with a condenser. In case Vertical Cone Reactor is providedwith the condenser, tert-butanol used as the solvent and apolyfluoroalkyl acrylate ester as the desired product were recovered inorder.

Example 2

Step (III):

360 g (0.69 mol) of the ester (C₈F₁₇CH₂CH₂OCOCH═CH₂) obtained in theabove step (II) as the product thereof, 180 g (0.55 mol) of stearylacrylate, 5.2 g of 3-chloro-2-hydroxypropyl methacrylate, 10.7 g ofN-methylolacrylamide, 95 g of an emulsifier, 750 g of water and 110 g ofdipropylene glycol monomethyl ether were charged in an autoclave ofglass (separate type glass apparatus) having a volume of 2 liter andthen preliminary emulsification was carried out at the temperature of 50to 55° C. for 30 minutes using an ultramixer. The particle size ofemulsion particles was measured by a particle size distributionmeasuring apparatus SALD-2100 (manufactured by Shimadzu Corporation). Asa result, it was within a range from 0.6 to 1.0 μm.

While maintaining the temperature of the preliminary emulsion at 45 to55° C., the preliminary emulsion was charged in a hopper of GAULINHOMOGENIZER (SUS, 1 liter) and high-pressure emulsification was carriedout. Although the emulsifying method includes a cycle emulsifying(circulating type) method and a pass emulsifying (passing type) method,the pass emulsifying method which is a more efficient method wasemployed in this Example. The emulsifying pressure was controlled to 450kg/cm². With respect to the emulsifying temperature, the emulsifyingmachine outlet port temperature is preferably maintained at 55±5° C.

The particle size of emulsion particles was measured by a particle sizedistribution measuring apparatus SALD-2100 (manufactured by ShimadzuCorporation). As a result, it was within a range from 0.03 to 0.20 μm.

The high-pressure emulsified product thus obtained was transferred to afour-necked flask having a volume of 1 liter and, after controlling theliquid temperature to a temperature within a range from 50 to 60° C.,dissolved oxygen was removed by replacement with nitrogen. Then, anazo-type polymerization initiator (V-50, manufactured by Wako PureChemicals Industries, Ltd.) was added and the copolymerization reactionwas carried out at 60° C. for one hour.

The particle size of the resulting polymer composition was measured by aparticle size distribution measuring apparatus SALD-2100 (manufacturedby Shimadzu Corporation). As a result, the resulting polymer compositionhad an average particle size of 0.08 μm. As a result of a centrifugalsedimentation test (carried out under the conditions of a diameter of 10cm at 5000 rpm for 30 minutes), no sediment was recognized.

Comparative Example 1

Using a conventional reaction apparatus shown in FIG. 2, a test forcomparison with the present invention was carried out.

Using, as an ester-forming reaction apparatus, an autoclave of SUShaving a volume of 1 liter, C₈F₁₇CH₂CH₂I (500 g), potassium acrylate (93g) and tert-butanol (350 g) were charged in this reaction apparatus andthe ester-forming reaction was carried out. The conditions of theester-forming reaction step were the same as those in

Example 1

To simulate the method of the prior art, tert-butanol having the watercontent of 2% by weight was used as tert-butanol in this ComparativeExample 1.

The analysis results of the product in the ester-forming reaction are asfollows.

An analysis revealed that (1) a conversion ratio of C₈F₁₇CH₂CH₂I is99.8%; and (2) a yield of C₈F₁₇CH₂CH₂OCOCH═CH₂ is 80%, a yield ofC₈F₁₇CH═CH₂ is 10% and a yield of C₈F₁₇CH₂CH₂OH is 6%.

943 g of the reaction product was collected by filtering through a 300mesh wedge filter. As a result of the measurement by means of gaschromatography, the yield of a polyfluoroalkyl acrylate ester was 80%.

Comparative Example 2

Those having the same charge composition as in Example 2 weretransferred to a four-necked flask having a volume of 1 liter afterpreliminary emulsification by a homomixer without carrying outhigh-pressure emulsification by GAULIN HOMOGENIZER. After controllingthe liquid temperature to a temperature within a range from 50 to 60°C., dissolved oxygen was removed by replacement with nitrogen. Then, anazo-type polymerization initiator (V-50, manufactured by Wako PureChemicals Industries, Ltd.) was added and the copolymerization reactionwas carried out at 60° C. for one hour.

The particle size of the resulting polymer composition was measured by aparticle size distribution measuring apparatus SALD-2100 (manufacturedby Shimadzu Corporation). As a result, the resulting polymer compositioncontained a polymer having a coarse particle size within a range from 1to several tens u m and also contained 65 g of coagulates having aparticle size within a range from 0.1 mm to several tens of mm in a wetstate.

As compared with Example 2, the yield loss is about 15%. Since thepolymer having a coarse particle size within a range from 1 μm toseveral tens of μm is liable to coagulate with a lapse of time to formparticles having a more large particle size, which are liable to formsediments or suspended materials, thus making it possible to causeworsening of the quality.

What is claimed is:
 1. A method of preparing a (perfluoroalkyl)ethyl(meth)acrylate ester, which comprises the steps of: (I) reacting a(perfluoroalkyl)ethyl iodide with a (meth)acrylic acid metal salt usinga solvent having a boiling point lower than that of the aimed product toobtain a reaction mixture containing a (perfluoroalkyl)ethyl(meth)acrylate ester and a metal iodide, as shown by the reaction scheme(Formula 1): C_(n)F_(2n+1)CH₂CH₂I+CH₂═CXCOOM→C_(n)F_(2n+i)CH₂CH₂OCOCX═CH₂+MI  (Formula 1) wherein X represents H orCH₃, n represents an integer within a range from 2 to 26, and Mrepresents an alkali metal element; and (II) heating the obtainedreaction mixture in the absence of water in order to evaporate andseparately recover the (perfluoroalkyl)ethyl (meth)acrylate from themetal iodide.
 2. The method according to claim 1, wherein apolyfluoroalkyl iodide of the formula C_(n)F_(2n+1)CH₂CH₂I is used inthe step (I), n being an integer within a range from 8 to
 20. 3. Themethod according to claim 1, wherein a salt of sodium or potassium isused as the (meth)acrylic acid metal salt in the step (I).
 4. A methodof preparing a fluorine-containing acrylic copolymer, which comprisesthe steps of: copolymerizing the (perfluoroalkyl)ethyl (meth)acrylateester prepared through the method of claim 1, with an ethylenicallyunsaturated compound capable of copolymerizing with the ester.
 5. Amethod of preparing a fluorine-containing acrylic copolymer, whichcomprises the steps of: copolymerizing the (perfluoroalkyl)ethyl(meth)acrylate ester prepared through the method of claim 2, with anethylenically unsaturated compound capable of copolymerizing with theester.
 6. A method of preparing a fluorine-containing acrylic copolymer,which comprises the steps of: copolymerizing the (perfluoroalkyl)ethyl(meth)acrylate ester prepared through the method of claim 3, with anethylenically unsaturated compound capable of copolymerizing with theester.
 7. The method according to claim 4, which comprises emulsifying asolution comprising a mixture of the (perfluoroalkyl)ethyl(meth)acrylate ester and the ethylenically unsaturated compound, whichare to be copolymerized, in a predetermined medium using a high-pressureemulsifying means to form emulsion particles having a particle sizewithin a range from 0.001 to 1 μm; and copolymerizing the emulsionparticles by emulsion polymerization.
 8. The method according to claim5, which comprises emulsifying a solution comprising a mixture of the(perfluoroalkyl)ethyl (meth)acrylate ester and the ethylenicallyunsaturated compound, which are to be copolymerized, in a predeterminedmedium using a high-pressure emulsifying means to form emulsionparticles having a particle size within a range from 0.001 to 1 μm; andcopolymerizing the emulsion particles by emulsion polymerization.
 9. Themethod according to claim 6, which comprises emulsifying a solutioncomprising a mixture of the (perfluoroalkyl)ethyl (meth)acrylate esterand the ethylenically unsaturated compound, which are to becopolymerized, in a predetermined medium using a high-pressureemulsifying means to form emulsion particles having a particle sizewithin a range from 0.001 to 1 μm; and copolymerizing the emulsionparticles by emulsion polymerization.
 10. The method according to claim7, wherein a microfluidizer is used as the high-pressure emulsifyingmeans.
 11. The method according to claim 8, wherein a microfluidizer isused as the high-pressure emulsifying means.
 12. The method according toclaim 9, wherein a microfluidizer is used as the high-pressureemulsifying means.
 13. The method according to claim 4, wherein at leastone compound selected from acrylates represented by the general formula(Formula 4): CH₂═CA¹COOA²  (Formula 4) wherein A¹ represents a hydrogenatom or a methyl group, A² represents an alkyl group represented byC_(m)H_(2m+1), and m represents an integer of 1 to 30, is used as theethylenically unsaturated compound.
 14. The method according to claim 6,wherein at least one compound selected from acrylates represented by thegeneral formula (Formula 4): CH₂═CA¹COOA²  (Formula 4) wherein A¹represents a hydrogen atom or a methyl group, A² represents an alkylgroup represented by C_(m)H_(2m+1), and m represents an integer of 1 to30, is used as the ethylenically unsaturated compound.
 15. The methodaccording to claim 8, wherein at least one compound selected fromacrylates represented by the general formula (Formula 4):CH₂═CA¹COOA²  (Formula 4) wherein A¹ represents a hydrogen atom or amethyl group, A² represents an alkyl group represented by C_(m)H_(2m+1),and m represents an integer of 1 to 30, is used as the ethylenicallyunsaturated compound.
 16. The method according to claim 9, wherein atleast one compound selected from acrylates represented by the generalformula (Formula 4): CH₂═CA¹COOA²  (Formula 4) wherein A¹ represents ahydrogen atom or a methyl group, A² represents an alkyl grouprepresented by C_(m)H_(2m+1), and m represents an integer of 1 to 30, isused as the ethylenically unsaturated compound.
 17. The method accordingto claim 10, wherein at least one compound selected from acrylatesrepresented by the general formula (Formula 4): CH₂═CA¹COOA²  (Formula4) wherein A¹ represents a hydrogen atom or a methyl group, A²represents an alkyl group represented by C_(m)H_(2m+1), and m representsan integer of 1 to 30, is used as the ethylenically unsaturatedcompound.
 18. The method according to claim 11, wherein at least onecompound selected from acrylates represented by the general formula(Formula 4): CH₂═CA¹COOA²  (Formula 4) wherein A¹ represents a hydrogenatom or a methyl group, A² represents an alkyl group represented byC_(m)H_(2m+1), and m represents an integer of 1 to 30, is used as theethylenically unsaturated compound.
 19. The method according to claim 1,wherein step (II) is conducted by heating the obtained reaction mixtureusing a stirring tank type evaporator having a jacketed heating means,having a helical blade as a stirring blade for high-viscosity materialand also having a reverse conical shape at the lower portion of theevaporator to evaporate the (perfluoroalkyl)ethyl (meth)acrylate ester,thereby separating from each other and recovering the(perfluoroalkyl)ethyl (meth)acrylate ester and the metal iodide.
 20. Themethod according to claim 1, wherein the water content in the reactionsystem is less than 1.0% by weight.